UC Davis viticulture and enology professor Linda Bisson smells a bottle of chardonnay that has varying types of yeast that produced different kinds of odors. Often, a basic smell test is used to see if a strain is working, which is later verified through more analytical trials. Sue Cockrell/Enterprise photo

New non-GMO yeast removes sulfur odor in wine

A winemaking yeast strain invented by a UC Davis researcher that removes the sulfur odor in wines has been patented and is undergoing development and marketing around the world and locally.

The non-genetically modified yeast was developed by Linda Bisson of the UCD department of viticulture and enology and is being marketed in partnership with Vancouver-based Renaissance BioScience Corp.

Local winemakers have heard of the new yeast and could be using the strain to make wine as early as this summer’s harvest, and some larger winemakers already have begun to use the new yeast in blends.

The yeast strain, used in fermentation to make wine, was bred through traditional methods to select for a new yeast that produces less hydrogen sulfide, which has an undesirable rotten egg smell, Bisson said. Even at low levels, hydrogen sulfide can mute the desired fruit characteristics of wines.

“The current way wineries can deal with (hydrogen sulfide) is by copper-treating the wine … keeping a low amount of copper in the wine,” Bisson said. “We wanted to make a strain to not have to manipulate the wine at all. Most winemakers are really minimalists and would rather have less interference, set up right from the beginning.”

News of the yeast has reached Winters-based Turkovich Family Wines, where winemaker Chris Turkovich said he will make a batch of wine from the strain during the August harvest.

“We use about 30 different yeast strains in our winery and are definitely interested in trying out any new strain that could produce a higher-quality wine,” Turkovich said.

“There is a big grape show next week in Sacramento, and we’re going to see what the availability is. We never know when it’s going to be commercially available,” said Turkovich, referring to the 2014 Unified Wine & Grape Symposium at the Sacramento Convention Center Jan. 28-30, where winemakers and grape growers will discuss new technologies in the field.

“Dr. Bisson’s discovery of this (hydrogen sulfide)-preventing trait was an enormous advance in winemaking quality and it’s a tribute to the importance of funding universities and the basic and applied research that many faculty like Dr. Bisson conduct,” said John Husnik, CEO of Renaissance BioScience Corp. Husnik could not provide names of winemakers using the new yeast in time for this article’s publication.

Bisson’s research began about a decade ago when her lab screened about 300 naturally occurring yeast strains from around the world, each of which produced varying amounts of hydrogen sulfide. One strain isolated by a UC Berkeley collaborator from the Tuscany region of Italy produced low levels of the odor-causer but was not strong enough in a fermenting culture to outcompete other naturally occurring organisms that usually make their way into the wine fermenting process.

Also important, Bisson added, was that the low-hydrogen sulfide strain was linked to a single gene, which could be transferred through breeding with another yeast strain — in this case, a stronger strain that could outcompete other organisms. The resulting offspring yeast retained improved strength as well as the low-hydrogen sulfide trait, and it was not genetically modified as the DNA within the naturally occurring gene remained wholly intact, Bisson said. Thus, the new strain is non-GMO.

While Turkovich said he will try the new yeast in winemaking, he recognizes that some winemakers could be skeptical in the beginning.

“Until it has a few years out in the industry … it will have to prove itself,” he said. “If it’s available, we’ll try it out on a small amount of wine and see if it works for our style of wine. We’ll definitely give it a shot.”